1. Field of the Invention
The present invention relates to the production of slide fasteners, and more particularly to a method and apparatus for automatically cutting a continuous slide fastener chain at longitudinally spaced successive element-free gap sections into individual slide fastener lengths.
2. Prior Art
U.S. Pat. No. 2,754,908 discloses an apparatus for automatically cutting a continuous slide fastener chain at longitudinally spaced successive element-free gap sections into individual slide fastener lengths. In this apparatus, the fastener chain is moved intermittently to a cutting station so that the movement of the fastener chain is halted every time each element-free gap section arrives at the cutting station. A cutting knife means, having coacting upper and lower blades, is disposed in the cutting station to sever the fastener chain across the successive element-free gap sections one after another in synchronization with intermittent movement of the fastener chain. The periodic termination of movement of the fastener chain is triggered by means of a pivotable stop member horizontally extending beneath the path of the fastener chain and having an upwardly angled tip end. The stop member is also horizontally movable between a first position upstream of the cutting station and a second position in the cutting station. Upon arrival of one of the successive element-free gap sections at the first position, the stop member is pivotally biased so that the tip end is inserted into the gap section, which is a space between a pair of opposed blank tape portions. The leading end of the succeeding pair of coupled fastener element then comes into engagement with the tip end of the stop member as the chain then continues its movement so that the stop member is moved to the second position in the cutting station. Movement of the stop member to its second position causes a switch to be actuated to terminate the movement of the fastener chain. The upper blade is then lowered to coact with the lower blade to sever the fastener chain across the element-free gap section.
One disadvantage with this apparatus is that, since the tip end of the stop member remains in the element-free gap section during this severing, the region at which the element-free gap section of the fastener chain can be severed is confined to only a limited region of the gap section.
Another problem with this prior art apparatus is that the endmost coupled elements or a bottom stop at the leading end of the succeeding pair of coupling elements would tend to be damaged by the tip end of the stop member. Further, there would be a danger that an accidental separation would occur along the leading end portion of the succeeding pair of coupling elements, causing inaccurate termination of the movement of the fastener chain. Consequently, uniform and adequate quality slide fasteners are difficult to achieve reliably with this prior art apparatus.
The present invention overcomes these drawbacks with such prior apparatus, such that element-free gap sections in a continuous slide fastener chain can be severed at any point therealong (even near the leading end of a succeeding pair of coupling elements) and the possibility of damage to or accidental separation of the endmost coupling elements or damage to a bottom end stop at the leading end of a succeeding pair of coupling elements is avoided, assuring uniform and adequate quality slide fasteners are produced.